[ViewVC] Diff of: cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.98 by root, Sat Dec 22 06:10:25 2007 UTC vs.
Revision 1.130 by root, Wed Feb 6 18:34:24 2008 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head1 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	#include <ev.h>	11	#include <ev.h>
12		12
13	ev_io stdin_watcher;	13	ev_io stdin_watcher;
14	ev_timer timeout_watcher;	14	ev_timer timeout_watcher;
…		…
65	You register interest in certain events by registering so-called I<event	65	You register interest in certain events by registering so-called I<event
66	watchers>, which are relatively small C structures you initialise with the	66	watchers>, which are relatively small C structures you initialise with the
67	details of the event, and then hand it over to libev by I<starting> the	67	details of the event, and then hand it over to libev by I<starting> the
68	watcher.	68	watcher.
69		69
70	=head1 FEATURES	70	=head2 FEATURES
71		71
72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
…		…
82		82
83	It also is quite fast (see this	83	It also is quite fast (see this
84	L<benchmark\|http://libev.schmorp.de/bench.html> comparing it to libevent	84	L<benchmark\|http://libev.schmorp.de/bench.html> comparing it to libevent
85	for example).	85	for example).
86		86
87	=head1 CONVENTIONS	87	=head2 CONVENTIONS
88		88
89	Libev is very configurable. In this manual the default configuration will	89	Libev is very configurable. In this manual the default configuration will
90	be described, which supports multiple event loops. For more info about	90	be described, which supports multiple event loops. For more info about
91	various configuration options please have a look at B<EMBED> section in	91	various configuration options please have a look at B<EMBED> section in
92	this manual. If libev was configured without support for multiple event	92	this manual. If libev was configured without support for multiple event
93	loops, then all functions taking an initial argument of name C<loop>	93	loops, then all functions taking an initial argument of name C<loop>
94	(which is always of type C<struct ev_loop *>) will not have this argument.	94	(which is always of type C<struct ev_loop *>) will not have this argument.
95		95
96	=head1 TIME REPRESENTATION	96	=head2 TIME REPRESENTATION
97		97
98	Libev represents time as a single floating point number, representing the	98	Libev represents time as a single floating point number, representing the
99	(fractional) number of seconds since the (POSIX) epoch (somewhere near	99	(fractional) number of seconds since the (POSIX) epoch (somewhere near
100	the beginning of 1970, details are complicated, don't ask). This type is	100	the beginning of 1970, details are complicated, don't ask). This type is
101	called C<ev_tstamp>, which is what you should use too. It usually aliases	101	called C<ev_tstamp>, which is what you should use too. It usually aliases
…		…
260	flags. If that is troubling you, check C<ev_backend ()> afterwards).	260	flags. If that is troubling you, check C<ev_backend ()> afterwards).
261		261
262	If you don't know what event loop to use, use the one returned from this	262	If you don't know what event loop to use, use the one returned from this
263	function.	263	function.
264		264
		265	The default loop is the only loop that can handle C<ev_signal> and
		266	C<ev_child> watchers, and to do this, it always registers a handler
		267	for C<SIGCHLD>. If this is a problem for your app you can either
		268	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		269	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		270	C<ev_default_init>.
		271
265	The flags argument can be used to specify special behaviour or specific	272	The flags argument can be used to specify special behaviour or specific
266	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	273	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
267		274
268	The following flags are supported:	275	The following flags are supported:
269		276
…		…
306	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	313	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
307		314
308	This is your standard select(2) backend. Not I<completely> standard, as	315	This is your standard select(2) backend. Not I<completely> standard, as
309	libev tries to roll its own fd_set with no limits on the number of fds,	316	libev tries to roll its own fd_set with no limits on the number of fds,
310	but if that fails, expect a fairly low limit on the number of fds when	317	but if that fails, expect a fairly low limit on the number of fds when
311	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	318	using this backend. It doesn't scale too well (O(highest_fd)), but its
312	the fastest backend for a low number of fds.	319	usually the fastest backend for a low number of (low-numbered :) fds.
		320
		321	To get good performance out of this backend you need a high amount of
		322	parallelity (most of the file descriptors should be busy). If you are
		323	writing a server, you should C<accept ()> in a loop to accept as many
		324	connections as possible during one iteration. You might also want to have
		325	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		326	readyness notifications you get per iteration.
313		327
314	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	328	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
315		329
316	And this is your standard poll(2) backend. It's more complicated than	330	And this is your standard poll(2) backend. It's more complicated
317	select, but handles sparse fds better and has no artificial limit on the	331	than select, but handles sparse fds better and has no artificial
318	number of fds you can use (except it will slow down considerably with a	332	limit on the number of fds you can use (except it will slow down
319	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	333	considerably with a lot of inactive fds). It scales similarly to select,
		334	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		335	performance tips.
320		336
321	=item C<EVBACKEND_EPOLL> (value 4, Linux)	337	=item C<EVBACKEND_EPOLL> (value 4, Linux)
322		338
323	For few fds, this backend is a bit little slower than poll and select,	339	For few fds, this backend is a bit little slower than poll and select,
324	but it scales phenomenally better. While poll and select usually scale	340	but it scales phenomenally better. While poll and select usually scale
325	like O(total_fds) where n is the total number of fds (or the highest fd),	341	like O(total_fds) where n is the total number of fds (or the highest fd),
326	epoll scales either O(1) or O(active_fds). The epoll design has a number	342	epoll scales either O(1) or O(active_fds). The epoll design has a number
327	of shortcomings, such as silently dropping events in some hard-to-detect	343	of shortcomings, such as silently dropping events in some hard-to-detect
328	cases and rewiring a syscall per fd change, no fork support and bad	344	cases and rewiring a syscall per fd change, no fork support and bad
329	support for dup:	345	support for dup.
330		346
331	While stopping, setting and starting an I/O watcher in the same iteration	347	While stopping, setting and starting an I/O watcher in the same iteration
332	will result in some caching, there is still a syscall per such incident	348	will result in some caching, there is still a syscall per such incident
333	(because the fd could point to a different file description now), so its	349	(because the fd could point to a different file description now), so its
334	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	350	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
…		…
336		352
337	Please note that epoll sometimes generates spurious notifications, so you	353	Please note that epoll sometimes generates spurious notifications, so you
338	need to use non-blocking I/O or other means to avoid blocking when no data	354	need to use non-blocking I/O or other means to avoid blocking when no data
339	(or space) is available.	355	(or space) is available.
340		356
		357	Best performance from this backend is achieved by not unregistering all
		358	watchers for a file descriptor until it has been closed, if possible, i.e.
		359	keep at least one watcher active per fd at all times.
		360
		361	While nominally embeddeble in other event loops, this feature is broken in
		362	all kernel versions tested so far.
		363
341	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	364	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
342		365
343	Kqueue deserves special mention, as at the time of this writing, it	366	Kqueue deserves special mention, as at the time of this writing, it
344	was broken on I<all> BSDs (usually it doesn't work with anything but	367	was broken on all BSDs except NetBSD (usually it doesn't work reliably
345	sockets and pipes, except on Darwin, where of course it's completely	368	with anything but sockets and pipes, except on Darwin, where of course
346	useless. On NetBSD, it seems to work for all the FD types I tested, so it
347	is used by default there). For this reason it's not being "autodetected"	369	it's completely useless). For this reason it's not being "autodetected"
348	unless you explicitly specify it explicitly in the flags (i.e. using	370	unless you explicitly specify it explicitly in the flags (i.e. using
349	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	371	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
350	system like NetBSD.	372	system like NetBSD.
351		373
		374	You still can embed kqueue into a normal poll or select backend and use it
		375	only for sockets (after having made sure that sockets work with kqueue on
		376	the target platform). See C<ev_embed> watchers for more info.
		377
352	It scales in the same way as the epoll backend, but the interface to the	378	It scales in the same way as the epoll backend, but the interface to the
353	kernel is more efficient (which says nothing about its actual speed,	379	kernel is more efficient (which says nothing about its actual speed, of
354	of course). While stopping, setting and starting an I/O watcher does	380	course). While stopping, setting and starting an I/O watcher does never
355	never cause an extra syscall as with epoll, it still adds up to two event	381	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
356	changes per incident, support for C<fork ()> is very bad and it drops fds	382	two event changes per incident, support for C<fork ()> is very bad and it
357	silently in similarly hard-to-detetc cases.	383	drops fds silently in similarly hard-to-detect cases.
		384
		385	This backend usually performs well under most conditions.
		386
		387	While nominally embeddable in other event loops, this doesn't work
		388	everywhere, so you might need to test for this. And since it is broken
		389	almost everywhere, you should only use it when you have a lot of sockets
		390	(for which it usually works), by embedding it into another event loop
		391	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		392	sockets.
358		393
359	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	394	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
360		395
361	This is not implemented yet (and might never be).	396	This is not implemented yet (and might never be, unless you send me an
		397	implementation). According to reports, C</dev/poll> only supports sockets
		398	and is not embeddable, which would limit the usefulness of this backend
		399	immensely.
362		400
363	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	401	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
364		402
365	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	403	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
366	it's really slow, but it still scales very well (O(active_fds)).	404	it's really slow, but it still scales very well (O(active_fds)).
367		405
368	Please note that solaris event ports can deliver a lot of spurious	406	Please note that solaris event ports can deliver a lot of spurious
369	notifications, so you need to use non-blocking I/O or other means to avoid	407	notifications, so you need to use non-blocking I/O or other means to avoid
370	blocking when no data (or space) is available.	408	blocking when no data (or space) is available.
371		409
		410	While this backend scales well, it requires one system call per active
		411	file descriptor per loop iteration. For small and medium numbers of file
		412	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		413	might perform better.
		414
		415	On the positive side, ignoring the spurious readyness notifications, this
		416	backend actually performed to specification in all tests and is fully
		417	embeddable, which is a rare feat among the OS-specific backends.
		418
372	=item C<EVBACKEND_ALL>	419	=item C<EVBACKEND_ALL>
373		420
374	Try all backends (even potentially broken ones that wouldn't be tried	421	Try all backends (even potentially broken ones that wouldn't be tried
375	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	422	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
376	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	423	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
377		424
		425	It is definitely not recommended to use this flag.
		426
378	=back	427	=back
379		428
380	If one or more of these are ored into the flags value, then only these	429	If one or more of these are ored into the flags value, then only these
381	backends will be tried (in the reverse order as given here). If none are	430	backends will be tried (in the reverse order as listed here). If none are
382	specified, most compiled-in backend will be tried, usually in reverse	431	specified, all backends in C<ev_recommended_backends ()> will be tried.
383	order of their flag values :)
384		432
385	The most typical usage is like this:	433	The most typical usage is like this:
386		434
387	if (!ev_default_loop (0))	435	if (!ev_default_loop (0))
388	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	436	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
435	Like C<ev_default_destroy>, but destroys an event loop created by an	483	Like C<ev_default_destroy>, but destroys an event loop created by an
436	earlier call to C<ev_loop_new>.	484	earlier call to C<ev_loop_new>.
437		485
438	=item ev_default_fork ()	486	=item ev_default_fork ()
439		487
		488	This function sets a flag that causes subsequent C<ev_loop> iterations
440	This function reinitialises the kernel state for backends that have	489	to reinitialise the kernel state for backends that have one. Despite the
441	one. Despite the name, you can call it anytime, but it makes most sense	490	name, you can call it anytime, but it makes most sense after forking, in
442	after forking, in either the parent or child process (or both, but that	491	the child process (or both child and parent, but that again makes little
443	again makes little sense).	492	sense). You I<must> call it in the child before using any of the libev
		493	functions, and it will only take effect at the next C<ev_loop> iteration.
444		494
445	You I<must> call this function in the child process after forking if and	495	On the other hand, you only need to call this function in the child
446	only if you want to use the event library in both processes. If you just	496	process if and only if you want to use the event library in the child. If
447	fork+exec, you don't have to call it.	497	you just fork+exec, you don't have to call it at all.
448		498
449	The function itself is quite fast and it's usually not a problem to call	499	The function itself is quite fast and it's usually not a problem to call
450	it just in case after a fork. To make this easy, the function will fit in	500	it just in case after a fork. To make this easy, the function will fit in
451	quite nicely into a call to C<pthread_atfork>:	501	quite nicely into a call to C<pthread_atfork>:
452		502
453	pthread_atfork (0, 0, ev_default_fork);	503	pthread_atfork (0, 0, ev_default_fork);
454
455	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
456	without calling this function, so if you force one of those backends you
457	do not need to care.
458		504
459	=item ev_loop_fork (loop)	505	=item ev_loop_fork (loop)
460		506
461	Like C<ev_default_fork>, but acts on an event loop created by	507	Like C<ev_default_fork>, but acts on an event loop created by
462	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	508	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
…		…
513	usually a better approach for this kind of thing.	559	usually a better approach for this kind of thing.
514		560
515	Here are the gory details of what C<ev_loop> does:	561	Here are the gory details of what C<ev_loop> does:
516		562
517	- Before the first iteration, call any pending watchers.	563	- Before the first iteration, call any pending watchers.
518	* If there are no active watchers (reference count is zero), return.	564	* If EVFLAG_FORKCHECK was used, check for a fork.
519	- Queue all prepare watchers and then call all outstanding watchers.	565	- If a fork was detected, queue and call all fork watchers.
		566	- Queue and call all prepare watchers.
520	- If we have been forked, recreate the kernel state.	567	- If we have been forked, recreate the kernel state.
521	- Update the kernel state with all outstanding changes.	568	- Update the kernel state with all outstanding changes.
522	- Update the "event loop time".	569	- Update the "event loop time".
523	- Calculate for how long to block.	570	- Calculate for how long to sleep or block, if at all
		571	(active idle watchers, EVLOOP_NONBLOCK or not having
		572	any active watchers at all will result in not sleeping).
		573	- Sleep if the I/O and timer collect interval say so.
524	- Block the process, waiting for any events.	574	- Block the process, waiting for any events.
525	- Queue all outstanding I/O (fd) events.	575	- Queue all outstanding I/O (fd) events.
526	- Update the "event loop time" and do time jump handling.	576	- Update the "event loop time" and do time jump handling.
527	- Queue all outstanding timers.	577	- Queue all outstanding timers.
528	- Queue all outstanding periodics.	578	- Queue all outstanding periodics.
529	- If no events are pending now, queue all idle watchers.	579	- If no events are pending now, queue all idle watchers.
530	- Queue all check watchers.	580	- Queue all check watchers.
531	- Call all queued watchers in reverse order (i.e. check watchers first).	581	- Call all queued watchers in reverse order (i.e. check watchers first).
532	Signals and child watchers are implemented as I/O watchers, and will	582	Signals and child watchers are implemented as I/O watchers, and will
533	be handled here by queueing them when their watcher gets executed.	583	be handled here by queueing them when their watcher gets executed.
534	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	584	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
535	were used, return, otherwise continue with step *.	585	were used, or there are no active watchers, return, otherwise
		586	continue with step *.
536		587
537	Example: Queue some jobs and then loop until no events are outsanding	588	Example: Queue some jobs and then loop until no events are outstanding
538	anymore.	589	anymore.
539		590
540	... queue jobs here, make sure they register event watchers as long	591	... queue jobs here, make sure they register event watchers as long
541	... as they still have work to do (even an idle watcher will do..)	592	... as they still have work to do (even an idle watcher will do..)
542	ev_loop (my_loop, 0);	593	ev_loop (my_loop, 0);
…		…
546		597
547	Can be used to make a call to C<ev_loop> return early (but only after it	598	Can be used to make a call to C<ev_loop> return early (but only after it
548	has processed all outstanding events). The C<how> argument must be either	599	has processed all outstanding events). The C<how> argument must be either
549	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	600	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
550	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	601	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		602
		603	This "unloop state" will be cleared when entering C<ev_loop> again.
551		604
552	=item ev_ref (loop)	605	=item ev_ref (loop)
553		606
554	=item ev_unref (loop)	607	=item ev_unref (loop)
555		608
…		…
560	returning, ev_unref() after starting, and ev_ref() before stopping it. For	613	returning, ev_unref() after starting, and ev_ref() before stopping it. For
561	example, libev itself uses this for its internal signal pipe: It is not	614	example, libev itself uses this for its internal signal pipe: It is not
562	visible to the libev user and should not keep C<ev_loop> from exiting if	615	visible to the libev user and should not keep C<ev_loop> from exiting if
563	no event watchers registered by it are active. It is also an excellent	616	no event watchers registered by it are active. It is also an excellent
564	way to do this for generic recurring timers or from within third-party	617	way to do this for generic recurring timers or from within third-party
565	libraries. Just remember to I<unref after start> and I<ref before stop>.	618	libraries. Just remember to I<unref after start> and I<ref before stop>
		619	(but only if the watcher wasn't active before, or was active before,
		620	respectively).
566		621
567	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	622	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
568	running when nothing else is active.	623	running when nothing else is active.
569		624
570	struct ev_signal exitsig;	625	struct ev_signal exitsig;
…		…
596	overhead for the actual polling but can deliver many events at once.	651	overhead for the actual polling but can deliver many events at once.
597		652
598	By setting a higher I<io collect interval> you allow libev to spend more	653	By setting a higher I<io collect interval> you allow libev to spend more
599	time collecting I/O events, so you can handle more events per iteration,	654	time collecting I/O events, so you can handle more events per iteration,
600	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	655	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
601	C<ev_timer>) will be not affected.	656	C<ev_timer>) will be not affected. Setting this to a non-null value will
		657	introduce an additional C<ev_sleep ()> call into most loop iterations.
602		658
603	Likewise, by setting a higher I<timeout collect interval> you allow libev	659	Likewise, by setting a higher I<timeout collect interval> you allow libev
604	to spend more time collecting timeouts, at the expense of increased	660	to spend more time collecting timeouts, at the expense of increased
605	latency (the watcher callback will be called later). C<ev_io> watchers	661	latency (the watcher callback will be called later). C<ev_io> watchers
606	will not be affected.	662	will not be affected. Setting this to a non-null value will not introduce
		663	any overhead in libev.
607		664
608	Many (busy) programs can usually benefit by setting the io collect	665	Many (busy) programs can usually benefit by setting the io collect
609	interval to a value near C<0.1> or so, which is often enough for	666	interval to a value near C<0.1> or so, which is often enough for
610	interactive servers (of course not for games), likewise for timeouts. It	667	interactive servers (of course not for games), likewise for timeouts. It
611	usually doesn't make much sense to set it to a lower value than C<0.01>,	668	usually doesn't make much sense to set it to a lower value than C<0.01>,
…		…
716		773
717	=item C<EV_FORK>	774	=item C<EV_FORK>
718		775
719	The event loop has been resumed in the child process after fork (see	776	The event loop has been resumed in the child process after fork (see
720	C<ev_fork>).	777	C<ev_fork>).
		778
		779	=item C<EV_ASYNC>
		780
		781	The given async watcher has been asynchronously notified (see C<ev_async>).
721		782
722	=item C<EV_ERROR>	783	=item C<EV_ERROR>
723		784
724	An unspecified error has occured, the watcher has been stopped. This might	785	An unspecified error has occured, the watcher has been stopped. This might
725	happen because the watcher could not be properly started because libev	786	happen because the watcher could not be properly started because libev
…		…
943	In general you can register as many read and/or write event watchers per	1004	In general you can register as many read and/or write event watchers per
944	fd as you want (as long as you don't confuse yourself). Setting all file	1005	fd as you want (as long as you don't confuse yourself). Setting all file
945	descriptors to non-blocking mode is also usually a good idea (but not	1006	descriptors to non-blocking mode is also usually a good idea (but not
946	required if you know what you are doing).	1007	required if you know what you are doing).
947		1008
948	You have to be careful with dup'ed file descriptors, though. Some backends
949	(the linux epoll backend is a notable example) cannot handle dup'ed file
950	descriptors correctly if you register interest in two or more fds pointing
951	to the same underlying file/socket/etc. description (that is, they share
952	the same underlying "file open").
953
954	If you must do this, then force the use of a known-to-be-good backend	1009	If you must do this, then force the use of a known-to-be-good backend
955	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1010	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
956	C<EVBACKEND_POLL>).	1011	C<EVBACKEND_POLL>).
957		1012
958	Another thing you have to watch out for is that it is quite easy to	1013	Another thing you have to watch out for is that it is quite easy to
…		…
992	optimisations to libev.	1047	optimisations to libev.
993		1048
994	=head3 The special problem of dup'ed file descriptors	1049	=head3 The special problem of dup'ed file descriptors
995		1050
996	Some backends (e.g. epoll), cannot register events for file descriptors,	1051	Some backends (e.g. epoll), cannot register events for file descriptors,
997	but only events for the underlying file descriptions. That menas when you	1052	but only events for the underlying file descriptions. That means when you
998	have C<dup ()>'ed file descriptors and register events for them, only one	1053	have C<dup ()>'ed file descriptors or weirder constellations, and register
999	file descriptor might actually receive events.	1054	events for them, only one file descriptor might actually receive events.
1000		1055
1001	There is no workaorund possible except not registering events	1056	There is no workaround possible except not registering events
1002	for potentially C<dup ()>'ed file descriptors or to resort to	1057	for potentially C<dup ()>'ed file descriptors, or to resort to
1003	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1058	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1004		1059
1005	=head3 The special problem of fork	1060	=head3 The special problem of fork
1006		1061
1007	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1062	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
…		…
1033	=item int events [read-only]	1088	=item int events [read-only]
1034		1089
1035	The events being watched.	1090	The events being watched.
1036		1091
1037	=back	1092	=back
		1093
		1094	=head3 Examples
1038		1095
1039	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1096	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1040	readable, but only once. Since it is likely line-buffered, you could	1097	readable, but only once. Since it is likely line-buffered, you could
1041	attempt to read a whole line in the callback.	1098	attempt to read a whole line in the callback.
1042		1099
…		…
1140	or C<ev_timer_again> is called and determines the next timeout (if any),	1197	or C<ev_timer_again> is called and determines the next timeout (if any),
1141	which is also when any modifications are taken into account.	1198	which is also when any modifications are taken into account.
1142		1199
1143	=back	1200	=back
1144		1201
		1202	=head3 Examples
		1203
1145	Example: Create a timer that fires after 60 seconds.	1204	Example: Create a timer that fires after 60 seconds.
1146		1205
1147	static void	1206	static void
1148	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)	1207	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
1149	{	1208	{
…		…
1306	When active, contains the absolute time that the watcher is supposed to	1365	When active, contains the absolute time that the watcher is supposed to
1307	trigger next.	1366	trigger next.
1308		1367
1309	=back	1368	=back
1310		1369
		1370	=head3 Examples
		1371
1311	Example: Call a callback every hour, or, more precisely, whenever the	1372	Example: Call a callback every hour, or, more precisely, whenever the
1312	system clock is divisible by 3600. The callback invocation times have	1373	system clock is divisible by 3600. The callback invocation times have
1313	potentially a lot of jittering, but good long-term stability.	1374	potentially a lot of jittering, but good long-term stability.
1314		1375
1315	static void	1376	static void
…		…
1381		1442
1382	=head3 Watcher-Specific Functions and Data Members	1443	=head3 Watcher-Specific Functions and Data Members
1383		1444
1384	=over 4	1445	=over 4
1385		1446
1386	=item ev_child_init (ev_child *, callback, int pid)	1447	=item ev_child_init (ev_child *, callback, int pid, int trace)
1387		1448
1388	=item ev_child_set (ev_child *, int pid)	1449	=item ev_child_set (ev_child *, int pid, int trace)
1389		1450
1390	Configures the watcher to wait for status changes of process C<pid> (or	1451	Configures the watcher to wait for status changes of process C<pid> (or
1391	I<any> process if C<pid> is specified as C<0>). The callback can look	1452	I<any> process if C<pid> is specified as C<0>). The callback can look
1392	at the C<rstatus> member of the C<ev_child> watcher structure to see	1453	at the C<rstatus> member of the C<ev_child> watcher structure to see
1393	the status word (use the macros from C<sys/wait.h> and see your systems	1454	the status word (use the macros from C<sys/wait.h> and see your systems
1394	C<waitpid> documentation). The C<rpid> member contains the pid of the	1455	C<waitpid> documentation). The C<rpid> member contains the pid of the
1395	process causing the status change.	1456	process causing the status change. C<trace> must be either C<0> (only
		1457	activate the watcher when the process terminates) or C<1> (additionally
		1458	activate the watcher when the process is stopped or continued).
1396		1459
1397	=item int pid [read-only]	1460	=item int pid [read-only]
1398		1461
1399	The process id this watcher watches out for, or C<0>, meaning any process id.	1462	The process id this watcher watches out for, or C<0>, meaning any process id.
1400		1463
…		…
1406		1469
1407	The process exit/trace status caused by C<rpid> (see your systems	1470	The process exit/trace status caused by C<rpid> (see your systems
1408	C<waitpid> and C<sys/wait.h> documentation for details).	1471	C<waitpid> and C<sys/wait.h> documentation for details).
1409		1472
1410	=back	1473	=back
		1474
		1475	=head3 Examples
1411		1476
1412	Example: Try to exit cleanly on SIGINT and SIGTERM.	1477	Example: Try to exit cleanly on SIGINT and SIGTERM.
1413		1478
1414	static void	1479	static void
1415	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1480	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
…		…
1456	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1521	semantics of C<ev_stat> watchers, which means that libev sometimes needs
1457	to fall back to regular polling again even with inotify, but changes are	1522	to fall back to regular polling again even with inotify, but changes are
1458	usually detected immediately, and if the file exists there will be no	1523	usually detected immediately, and if the file exists there will be no
1459	polling.	1524	polling.
1460		1525
		1526	=head3 Inotify
		1527
		1528	When C<inotify (7)> support has been compiled into libev (generally only
		1529	available on Linux) and present at runtime, it will be used to speed up
		1530	change detection where possible. The inotify descriptor will be created lazily
		1531	when the first C<ev_stat> watcher is being started.
		1532
		1533	Inotify presense does not change the semantics of C<ev_stat> watchers
		1534	except that changes might be detected earlier, and in some cases, to avoid
		1535	making regular C<stat> calls. Even in the presense of inotify support
		1536	there are many cases where libev has to resort to regular C<stat> polling.
		1537
		1538	(There is no support for kqueue, as apparently it cannot be used to
		1539	implement this functionality, due to the requirement of having a file
		1540	descriptor open on the object at all times).
		1541
		1542	=head3 The special problem of stat time resolution
		1543
		1544	The C<stat ()> syscall only supports full-second resolution portably, and
		1545	even on systems where the resolution is higher, many filesystems still
		1546	only support whole seconds.
		1547
		1548	That means that, if the time is the only thing that changes, you might
		1549	miss updates: on the first update, C<ev_stat> detects a change and calls
		1550	your callback, which does something. When there is another update within
		1551	the same second, C<ev_stat> will be unable to detect it.
		1552
		1553	The solution to this is to delay acting on a change for a second (or till
		1554	the next second boundary), using a roughly one-second delay C<ev_timer>
		1555	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1556	is added to work around small timing inconsistencies of some operating
		1557	systems.
		1558
1461	=head3 Watcher-Specific Functions and Data Members	1559	=head3 Watcher-Specific Functions and Data Members
1462		1560
1463	=over 4	1561	=over 4
1464		1562
1465	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)	1563	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)
…		…
1502	=item const char *path [read-only]	1600	=item const char *path [read-only]
1503		1601
1504	The filesystem path that is being watched.	1602	The filesystem path that is being watched.
1505		1603
1506	=back	1604	=back
		1605
		1606	=head3 Examples
1507		1607
1508	Example: Watch C</etc/passwd> for attribute changes.	1608	Example: Watch C</etc/passwd> for attribute changes.
1509		1609
1510	static void	1610	static void
1511	passwd_cb (struct ev_loop loop, ev_stat w, int revents)	1611	passwd_cb (struct ev_loop loop, ev_stat w, int revents)
…		…
1524	}	1624	}
1525		1625
1526	...	1626	...
1527	ev_stat passwd;	1627	ev_stat passwd;
1528		1628
1529	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1629	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1530	ev_stat_start (loop, &passwd);	1630	ev_stat_start (loop, &passwd);
		1631
		1632	Example: Like above, but additionally use a one-second delay so we do not
		1633	miss updates (however, frequent updates will delay processing, too, so
		1634	one might do the work both on C<ev_stat> callback invocation I<and> on
		1635	C<ev_timer> callback invocation).
		1636
		1637	static ev_stat passwd;
		1638	static ev_timer timer;
		1639
		1640	static void
		1641	timer_cb (EV_P_ ev_timer *w, int revents)
		1642	{
		1643	ev_timer_stop (EV_A_ w);
		1644
		1645	/* now it's one second after the most recent passwd change */
		1646	}
		1647
		1648	static void
		1649	stat_cb (EV_P_ ev_stat *w, int revents)
		1650	{
		1651	/* reset the one-second timer */
		1652	ev_timer_again (EV_A_ &timer);
		1653	}
		1654
		1655	...
		1656	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1657	ev_stat_start (loop, &passwd);
		1658	ev_timer_init (&timer, timer_cb, 0., 1.01);
1531		1659
1532		1660
1533	=head2 C<ev_idle> - when you've got nothing better to do...	1661	=head2 C<ev_idle> - when you've got nothing better to do...
1534		1662
1535	Idle watchers trigger events when no other events of the same or higher	1663	Idle watchers trigger events when no other events of the same or higher
…		…
1561	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1689	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1562	believe me.	1690	believe me.
1563		1691
1564	=back	1692	=back
1565		1693
		1694	=head3 Examples
		1695
1566	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1696	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1567	callback, free it. Also, use no error checking, as usual.	1697	callback, free it. Also, use no error checking, as usual.
1568		1698
1569	static void	1699	static void
1570	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)	1700	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
1571	{	1701	{
1572	free (w);	1702	free (w);
1573	// now do something you wanted to do when the program has	1703	// now do something you wanted to do when the program has
1574	// no longer asnything immediate to do.	1704	// no longer anything immediate to do.
1575	}	1705	}
1576		1706
1577	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1707	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1578	ev_idle_init (idle_watcher, idle_cb);	1708	ev_idle_init (idle_watcher, idle_cb);
1579	ev_idle_start (loop, idle_cb);	1709	ev_idle_start (loop, idle_cb);
…		…
1621		1751
1622	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	1752	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1623	priority, to ensure that they are being run before any other watchers	1753	priority, to ensure that they are being run before any other watchers
1624	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	1754	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1625	too) should not activate ("feed") events into libev. While libev fully	1755	too) should not activate ("feed") events into libev. While libev fully
1626	supports this, they will be called before other C<ev_check> watchers did	1756	supports this, they will be called before other C<ev_check> watchers
1627	their job. As C<ev_check> watchers are often used to embed other event	1757	did their job. As C<ev_check> watchers are often used to embed other
1628	loops those other event loops might be in an unusable state until their	1758	(non-libev) event loops those other event loops might be in an unusable
1629	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	1759	state until their C<ev_check> watcher ran (always remind yourself to
1630	others).	1760	coexist peacefully with others).
1631		1761
1632	=head3 Watcher-Specific Functions and Data Members	1762	=head3 Watcher-Specific Functions and Data Members
1633		1763
1634	=over 4	1764	=over 4
1635		1765
…		…
1640	Initialises and configures the prepare or check watcher - they have no	1770	Initialises and configures the prepare or check watcher - they have no
1641	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1771	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1642	macros, but using them is utterly, utterly and completely pointless.	1772	macros, but using them is utterly, utterly and completely pointless.
1643		1773
1644	=back	1774	=back
		1775
		1776	=head3 Examples
1645		1777
1646	There are a number of principal ways to embed other event loops or modules	1778	There are a number of principal ways to embed other event loops or modules
1647	into libev. Here are some ideas on how to include libadns into libev	1779	into libev. Here are some ideas on how to include libadns into libev
1648	(there is a Perl module named C<EV::ADNS> that does this, which you could	1780	(there is a Perl module named C<EV::ADNS> that does this, which you could
1649	use for an actually working example. Another Perl module named C<EV::Glib>	1781	use for an actually working example. Another Perl module named C<EV::Glib>
…		…
1774	=head2 C<ev_embed> - when one backend isn't enough...	1906	=head2 C<ev_embed> - when one backend isn't enough...
1775		1907
1776	This is a rather advanced watcher type that lets you embed one event loop	1908	This is a rather advanced watcher type that lets you embed one event loop
1777	into another (currently only C<ev_io> events are supported in the embedded	1909	into another (currently only C<ev_io> events are supported in the embedded
1778	loop, other types of watchers might be handled in a delayed or incorrect	1910	loop, other types of watchers might be handled in a delayed or incorrect
1779	fashion and must not be used). (See portability notes, below).	1911	fashion and must not be used).
1780		1912
1781	There are primarily two reasons you would want that: work around bugs and	1913	There are primarily two reasons you would want that: work around bugs and
1782	prioritise I/O.	1914	prioritise I/O.
1783		1915
1784	As an example for a bug workaround, the kqueue backend might only support	1916	As an example for a bug workaround, the kqueue backend might only support
…		…
1818	portable one.	1950	portable one.
1819		1951
1820	So when you want to use this feature you will always have to be prepared	1952	So when you want to use this feature you will always have to be prepared
1821	that you cannot get an embeddable loop. The recommended way to get around	1953	that you cannot get an embeddable loop. The recommended way to get around
1822	this is to have a separate variables for your embeddable loop, try to	1954	this is to have a separate variables for your embeddable loop, try to
1823	create it, and if that fails, use the normal loop for everything:	1955	create it, and if that fails, use the normal loop for everything.
		1956
		1957	=head3 Watcher-Specific Functions and Data Members
		1958
		1959	=over 4
		1960
		1961	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
		1962
		1963	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)
		1964
		1965	Configures the watcher to embed the given loop, which must be
		1966	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1967	invoked automatically, otherwise it is the responsibility of the callback
		1968	to invoke it (it will continue to be called until the sweep has been done,
		1969	if you do not want thta, you need to temporarily stop the embed watcher).
		1970
		1971	=item ev_embed_sweep (loop, ev_embed *)
		1972
		1973	Make a single, non-blocking sweep over the embedded loop. This works
		1974	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1975	apropriate way for embedded loops.
		1976
		1977	=item struct ev_loop *other [read-only]
		1978
		1979	The embedded event loop.
		1980
		1981	=back
		1982
		1983	=head3 Examples
		1984
		1985	Example: Try to get an embeddable event loop and embed it into the default
		1986	event loop. If that is not possible, use the default loop. The default
		1987	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		1988	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		1989	used).
1824		1990
1825	struct ev_loop *loop_hi = ev_default_init (0);	1991	struct ev_loop *loop_hi = ev_default_init (0);
1826	struct ev_loop *loop_lo = 0;	1992	struct ev_loop *loop_lo = 0;
1827	struct ev_embed embed;	1993	struct ev_embed embed;
1828		1994
…		…
1839	ev_embed_start (loop_hi, &embed);	2005	ev_embed_start (loop_hi, &embed);
1840	}	2006	}
1841	else	2007	else
1842	loop_lo = loop_hi;	2008	loop_lo = loop_hi;
1843		2009
1844	=head2 Portability notes	2010	Example: Check if kqueue is available but not recommended and create
		2011	a kqueue backend for use with sockets (which usually work with any
		2012	kqueue implementation). Store the kqueue/socket-only event loop in
		2013	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1845		2014
1846	Kqueue is nominally embeddable, but this is broken on all BSDs that I	2015	struct ev_loop *loop = ev_default_init (0);
1847	tried, in various ways. Usually the embedded event loop will simply never	2016	struct ev_loop *loop_socket = 0;
1848	receive events, sometimes it will only trigger a few times, sometimes in a	2017	struct ev_embed embed;
1849	loop. Epoll is also nominally embeddable, but many Linux kernel versions	2018
1850	will always eport the epoll fd as ready, even when no events are pending.	2019	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2020	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2021	{
		2022	ev_embed_init (&embed, 0, loop_socket);
		2023	ev_embed_start (loop, &embed);
		2024	}
1851		2025
1852	While libev allows embedding these backends (they are contained in	2026	if (!loop_socket)
1853	C<ev_embeddable_backends ()>), take extreme care that it will actually	2027	loop_socket = loop;
1854	work.
1855		2028
1856	When in doubt, create a dynamic event loop forced to use sockets (this	2029	// now use loop_socket for all sockets, and loop for everything else
1857	usually works) and possibly another thread and a pipe or so to report to
1858	your main event loop.
1859
1860	=head3 Watcher-Specific Functions and Data Members
1861
1862	=over 4
1863
1864	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
1865
1866	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)
1867
1868	Configures the watcher to embed the given loop, which must be
1869	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1870	invoked automatically, otherwise it is the responsibility of the callback
1871	to invoke it (it will continue to be called until the sweep has been done,
1872	if you do not want thta, you need to temporarily stop the embed watcher).
1873
1874	=item ev_embed_sweep (loop, ev_embed *)
1875
1876	Make a single, non-blocking sweep over the embedded loop. This works
1877	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1878	apropriate way for embedded loops.
1879
1880	=item struct ev_loop *other [read-only]
1881
1882	The embedded event loop.
1883
1884	=back
1885		2030
1886		2031
1887	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2032	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1888		2033
1889	Fork watchers are called when a C<fork ()> was detected (usually because	2034	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1905	believe me.	2050	believe me.
1906		2051
1907	=back	2052	=back
1908		2053
1909		2054
		2055	=head2 C<ev_async> - how to wake up another event loop
		2056
		2057	In general, you cannot use an C<ev_loop> from multiple threads or other
		2058	asynchronous sources such as signal handlers (as opposed to multiple event
		2059	loops - those are of course safe to use in different threads).
		2060
		2061	Sometimes, however, you need to wake up another event loop you do not
		2062	control, for example because it belongs to another thread. This is what
		2063	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2064	can signal it by calling C<ev_async_send>, which is thread- and signal
		2065	safe.
		2066
		2067	This functionality is very similar to C<ev_signal> watchers, as signals,
		2068	too, are asynchronous in nature, and signals, too, will be compressed
		2069	(i.e. the number of callback invocations may be less than the number of
		2070	C<ev_async_sent> calls).
		2071
		2072	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2073	just the default loop.
		2074
		2075	=head3 Queueing
		2076
		2077	C<ev_async> does not support queueing of data in any way. The reason
		2078	is that the author does not know of a simple (or any) algorithm for a
		2079	multiple-writer-single-reader queue that works in all cases and doesn't
		2080	need elaborate support such as pthreads.
		2081
		2082	That means that if you want to queue data, you have to provide your own
		2083	queue. But at least I can tell you would implement locking around your
		2084	queue:
		2085
		2086	=over 4
		2087
		2088	=item queueing from a signal handler context
		2089
		2090	To implement race-free queueing, you simply add to the queue in the signal
		2091	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2092	some fictitiuous SIGUSR1 handler:
		2093
		2094	static ev_async mysig;
		2095
		2096	static void
		2097	sigusr1_handler (void)
		2098	{
		2099	sometype data;
		2100
		2101	// no locking etc.
		2102	queue_put (data);
		2103	ev_async_send (DEFAULT_ &mysig);
		2104	}
		2105
		2106	static void
		2107	mysig_cb (EV_P_ ev_async *w, int revents)
		2108	{
		2109	sometype data;
		2110	sigset_t block, prev;
		2111
		2112	sigemptyset (&block);
		2113	sigaddset (&block, SIGUSR1);
		2114	sigprocmask (SIG_BLOCK, &block, &prev);
		2115
		2116	while (queue_get (&data))
		2117	process (data);
		2118
		2119	if (sigismember (&prev, SIGUSR1)
		2120	sigprocmask (SIG_UNBLOCK, &block, 0);
		2121	}
		2122
		2123	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2124	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2125	either...).
		2126
		2127	=item queueing from a thread context
		2128
		2129	The strategy for threads is different, as you cannot (easily) block
		2130	threads but you can easily preempt them, so to queue safely you need to
		2131	employ a traditional mutex lock, such as in this pthread example:
		2132
		2133	static ev_async mysig;
		2134	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2135
		2136	static void
		2137	otherthread (void)
		2138	{
		2139	// only need to lock the actual queueing operation
		2140	pthread_mutex_lock (&mymutex);
		2141	queue_put (data);
		2142	pthread_mutex_unlock (&mymutex);
		2143
		2144	ev_async_send (DEFAULT_ &mysig);
		2145	}
		2146
		2147	static void
		2148	mysig_cb (EV_P_ ev_async *w, int revents)
		2149	{
		2150	pthread_mutex_lock (&mymutex);
		2151
		2152	while (queue_get (&data))
		2153	process (data);
		2154
		2155	pthread_mutex_unlock (&mymutex);
		2156	}
		2157
		2158	=back
		2159
		2160
		2161	=head3 Watcher-Specific Functions and Data Members
		2162
		2163	=over 4
		2164
		2165	=item ev_async_init (ev_async *, callback)
		2166
		2167	Initialises and configures the async watcher - it has no parameters of any
		2168	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2169	believe me.
		2170
		2171	=item ev_async_send (loop, ev_async *)
		2172
		2173	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2174	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2175	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2176	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
		2177	section below on what exactly this means).
		2178
		2179	This call incurs the overhead of a syscall only once per loop iteration,
		2180	so while the overhead might be noticable, it doesn't apply to repeated
		2181	calls to C<ev_async_send>.
		2182
		2183	=back
		2184
		2185
1910	=head1 OTHER FUNCTIONS	2186	=head1 OTHER FUNCTIONS
1911		2187
1912	There are some other functions of possible interest. Described. Here. Now.	2188	There are some other functions of possible interest. Described. Here. Now.
1913		2189
1914	=over 4	2190	=over 4
…		…
2141	Example: Define a class with an IO and idle watcher, start one of them in	2417	Example: Define a class with an IO and idle watcher, start one of them in
2142	the constructor.	2418	the constructor.
2143		2419
2144	class myclass	2420	class myclass
2145	{	2421	{
2146	ev_io io; void io_cb (ev::io &w, int revents);	2422	ev::io io; void io_cb (ev::io &w, int revents);
2147	ev_idle idle void idle_cb (ev::idle &w, int revents);	2423	ev:idle idle void idle_cb (ev::idle &w, int revents);
2148		2424
2149	myclass ();	2425	myclass (int fd)
2150	}
2151
2152	myclass::myclass (int fd)
2153	{	2426	{
2154	io .set <myclass, &myclass::io_cb > (this);	2427	io .set <myclass, &myclass::io_cb > (this);
2155	idle.set <myclass, &myclass::idle_cb> (this);	2428	idle.set <myclass, &myclass::idle_cb> (this);
2156		2429
2157	io.start (fd, ev::READ);	2430	io.start (fd, ev::READ);
		2431	}
2158	}	2432	};
2159		2433
2160		2434
2161	=head1 MACRO MAGIC	2435	=head1 MACRO MAGIC
2162		2436
2163	Libev can be compiled with a variety of options, the most fundamantal	2437	Libev can be compiled with a variety of options, the most fundamantal
…		…
2368	wants osf handles on win32 (this is the case when the select to	2642	wants osf handles on win32 (this is the case when the select to
2369	be used is the winsock select). This means that it will call	2643	be used is the winsock select). This means that it will call
2370	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2644	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2371	it is assumed that all these functions actually work on fds, even	2645	it is assumed that all these functions actually work on fds, even
2372	on win32. Should not be defined on non-win32 platforms.	2646	on win32. Should not be defined on non-win32 platforms.
		2647
		2648	=item EV_FD_TO_WIN32_HANDLE
		2649
		2650	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2651	file descriptors to socket handles. When not defining this symbol (the
		2652	default), then libev will call C<_get_osfhandle>, which is usually
		2653	correct. In some cases, programs use their own file descriptor management,
		2654	in which case they can provide this function to map fds to socket handles.
2373		2655
2374	=item EV_USE_POLL	2656	=item EV_USE_POLL
2375		2657
2376	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2658	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2377	backend. Otherwise it will be enabled on non-win32 platforms. It	2659	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2411		2693
2412	If defined to be C<1>, libev will compile in support for the Linux inotify	2694	If defined to be C<1>, libev will compile in support for the Linux inotify
2413	interface to speed up C<ev_stat> watchers. Its actual availability will	2695	interface to speed up C<ev_stat> watchers. Its actual availability will
2414	be detected at runtime.	2696	be detected at runtime.
2415		2697
		2698	=item EV_ATOMIC_T
		2699
		2700	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2701	access is atomic with respect to other threads or signal contexts. No such
		2702	type is easily found in the C language, so you can provide your own type
		2703	that you know is safe for your purposes. It is used both for signal handler "locking"
		2704	as well as for signal and thread safety in C<ev_async> watchers.
		2705
		2706	In the absense of this define, libev will use C<sig_atomic_t volatile>
		2707	(from F<signal.h>), which is usually good enough on most platforms.
		2708
2416	=item EV_H	2709	=item EV_H
2417		2710
2418	The name of the F<ev.h> header file used to include it. The default if	2711	The name of the F<ev.h> header file used to include it. The default if
2419	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2712	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2420	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2713	used to virtually rename the F<ev.h> header file in case of conflicts.
2421		2714
2422	=item EV_CONFIG_H	2715	=item EV_CONFIG_H
2423		2716
2424	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2717	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2425	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2718	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2426	C<EV_H>, above.	2719	C<EV_H>, above.
2427		2720
2428	=item EV_EVENT_H	2721	=item EV_EVENT_H
2429		2722
2430	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2723	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2431	of how the F<event.h> header can be found.	2724	of how the F<event.h> header can be found, the default is C<"event.h">.
2432		2725
2433	=item EV_PROTOTYPES	2726	=item EV_PROTOTYPES
2434		2727
2435	If defined to be C<0>, then F<ev.h> will not define any function	2728	If defined to be C<0>, then F<ev.h> will not define any function
2436	prototypes, but still define all the structs and other symbols. This is	2729	prototypes, but still define all the structs and other symbols. This is
…		…
2487	=item EV_FORK_ENABLE	2780	=item EV_FORK_ENABLE
2488		2781
2489	If undefined or defined to be C<1>, then fork watchers are supported. If	2782	If undefined or defined to be C<1>, then fork watchers are supported. If
2490	defined to be C<0>, then they are not.	2783	defined to be C<0>, then they are not.
2491		2784
		2785	=item EV_ASYNC_ENABLE
		2786
		2787	If undefined or defined to be C<1>, then async watchers are supported. If
		2788	defined to be C<0>, then they are not.
		2789
2492	=item EV_MINIMAL	2790	=item EV_MINIMAL
2493		2791
2494	If you need to shave off some kilobytes of code at the expense of some	2792	If you need to shave off some kilobytes of code at the expense of some
2495	speed, define this symbol to C<1>. Currently only used for gcc to override	2793	speed, define this symbol to C<1>. Currently only used for gcc to override
2496	some inlining decisions, saves roughly 30% codesize of amd64.	2794	some inlining decisions, saves roughly 30% codesize of amd64.
…		…
2502	than enough. If you need to manage thousands of children you might want to	2800	than enough. If you need to manage thousands of children you might want to
2503	increase this value (I<must> be a power of two).	2801	increase this value (I<must> be a power of two).
2504		2802
2505	=item EV_INOTIFY_HASHSIZE	2803	=item EV_INOTIFY_HASHSIZE
2506		2804
2507	C<ev_staz> watchers use a small hash table to distribute workload by	2805	C<ev_stat> watchers use a small hash table to distribute workload by
2508	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	2806	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2509	usually more than enough. If you need to manage thousands of C<ev_stat>	2807	usually more than enough. If you need to manage thousands of C<ev_stat>
2510	watchers you might want to increase this value (I<must> be a power of	2808	watchers you might want to increase this value (I<must> be a power of
2511	two).	2809	two).
2512		2810
…		…
2608		2906
2609	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2907	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2610		2908
2611	This means that, when you have a watcher that triggers in one hour and	2909	This means that, when you have a watcher that triggers in one hour and
2612	there are 100 watchers that would trigger before that then inserting will	2910	there are 100 watchers that would trigger before that then inserting will
2613	have to skip those 100 watchers.	2911	have to skip roughly seven (C<ld 100>) of these watchers.
2614		2912
2615	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2913	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2616		2914
2617	That means that for changing a timer costs less than removing/adding them	2915	That means that changing a timer costs less than removing/adding them
2618	as only the relative motion in the event queue has to be paid for.	2916	as only the relative motion in the event queue has to be paid for.
2619		2917
2620	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2918	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2621		2919
2622	These just add the watcher into an array or at the head of a list.	2920	These just add the watcher into an array or at the head of a list.
		2921
2623	=item Stopping check/prepare/idle watchers: O(1)	2922	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2624		2923
2625	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	2924	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2626		2925
2627	These watchers are stored in lists then need to be walked to find the	2926	These watchers are stored in lists then need to be walked to find the
2628	correct watcher to remove. The lists are usually short (you don't usually	2927	correct watcher to remove. The lists are usually short (you don't usually
2629	have many watchers waiting for the same fd or signal).	2928	have many watchers waiting for the same fd or signal).
2630		2929
2631	=item Finding the next timer per loop iteration: O(1)	2930	=item Finding the next timer in each loop iteration: O(1)
		2931
		2932	By virtue of using a binary heap, the next timer is always found at the
		2933	beginning of the storage array.
2632		2934
2633	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2935	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2634		2936
2635	A change means an I/O watcher gets started or stopped, which requires	2937	A change means an I/O watcher gets started or stopped, which requires
2636	libev to recalculate its status (and possibly tell the kernel).	2938	libev to recalculate its status (and possibly tell the kernel, depending
		2939	on backend and wether C<ev_io_set> was used).
2637		2940
2638	=item Activating one watcher: O(1)	2941	=item Activating one watcher (putting it into the pending state): O(1)
2639		2942
2640	=item Priority handling: O(number_of_priorities)	2943	=item Priority handling: O(number_of_priorities)
2641		2944
2642	Priorities are implemented by allocating some space for each	2945	Priorities are implemented by allocating some space for each
2643	priority. When doing priority-based operations, libev usually has to	2946	priority. When doing priority-based operations, libev usually has to
2644	linearly search all the priorities.	2947	linearly search all the priorities, but starting/stopping and activating
		2948	watchers becomes O(1) w.r.t. priority handling.
		2949
		2950	=item Sending an ev_async: O(1)
		2951
		2952	=item Processing ev_async_send: O(number_of_async_watchers)
		2953
		2954	=item Processing signals: O(max_signal_number)
		2955
		2956	Sending involves a syscall I<iff> there were no other C<ev_async_send>
		2957	calls in the current loop iteration. Checking for async and signal events
		2958	involves iterating over all running async watchers or all signal numbers.
2645		2959
2646	=back	2960	=back
2647		2961
2648		2962
		2963	=head1 Win32 platform limitations and workarounds
		2964
		2965	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		2966	requires, and its I/O model is fundamentally incompatible with the POSIX
		2967	model. Libev still offers limited functionality on this platform in
		2968	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		2969	descriptors. This only applies when using Win32 natively, not when using
		2970	e.g. cygwin.
		2971
		2972	There is no supported compilation method available on windows except
		2973	embedding it into other applications.
		2974
		2975	Due to the many, low, and arbitrary limits on the win32 platform and the
		2976	abysmal performance of winsockets, using a large number of sockets is not
		2977	recommended (and not reasonable). If your program needs to use more than
		2978	a hundred or so sockets, then likely it needs to use a totally different
		2979	implementation for windows, as libev offers the POSIX model, which cannot
		2980	be implemented efficiently on windows (microsoft monopoly games).
		2981
		2982	=over 4
		2983
		2984	=item The winsocket select function
		2985
		2986	The winsocket C<select> function doesn't follow POSIX in that it requires
		2987	socket I<handles> and not socket I<file descriptors>. This makes select
		2988	very inefficient, and also requires a mapping from file descriptors
		2989	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		2990	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		2991	symbols for more info.
		2992
		2993	The configuration for a "naked" win32 using the microsoft runtime
		2994	libraries and raw winsocket select is:
		2995
		2996	#define EV_USE_SELECT 1
		2997	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		2998
		2999	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3000	complexity in the O(n²) range when using win32.
		3001
		3002	=item Limited number of file descriptors
		3003
		3004	Windows has numerous arbitrary (and low) limits on things. Early versions
		3005	of winsocket's select only supported waiting for a max. of C<64> handles
		3006	(probably owning to the fact that all windows kernels can only wait for
		3007	C<64> things at the same time internally; microsoft recommends spawning a
		3008	chain of threads and wait for 63 handles and the previous thread in each).
		3009
		3010	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3011	to some high number (e.g. C<2048>) before compiling the winsocket select
		3012	call (which might be in libev or elsewhere, for example, perl does its own
		3013	select emulation on windows).
		3014
		3015	Another limit is the number of file descriptors in the microsoft runtime
		3016	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3017	or something like this inside microsoft). You can increase this by calling
		3018	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3019	arbitrary limit), but is broken in many versions of the microsoft runtime
		3020	libraries.
		3021
		3022	This might get you to about C<512> or C<2048> sockets (depending on
		3023	windows version and/or the phase of the moon). To get more, you need to
		3024	wrap all I/O functions and provide your own fd management, but the cost of
		3025	calling select (O(n²)) will likely make this unworkable.
		3026
		3027	=back
		3028
		3029
2649	=head1 AUTHOR	3030	=head1 AUTHOR
2650		3031
2651	Marc Lehmann <libev@schmorp.de>.	3032	Marc Lehmann <libev@schmorp.de>.
2652		3033

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Comparing libev/ev.pod (file contents): Revision 1.98 by root, Sat Dec 22 06:10:25 2007 UTC vs. Revision 1.130 by root, Wed Feb 6 18:34:24 2008 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.98 by root, Sat Dec 22 06:10:25 2007 UTC vs.
Revision 1.130 by root, Wed Feb 6 18:34:24 2008 UTC